Latency controlled redundant routing

ABSTRACT

Redundant, non-overlapping paths or routes for a sensor signal in a mesh network are selected based on predetermined metrics. In one embodiment, a wireless sensor transmits a signal that is received by two separate infrastructure nodes. The signal is retransmitted by the two intermediate nodes via the selected non-overlapping routes to a controller node. Routes are identified for at least two infrastructure nodes that receive signals from an added sensor. Performance metrics are calculated for each route. The two routes with the best performance metrics are selected in one embodiment.

FIELD OF THE INVENTION

The present invention relates to robust routing in wireless networks,and in particular to latency control and fault containment in redundantwireless route determination.

BACKGROUND OF THE INVENTION

Wireless leaf nodes, such as sensors are networked via multipleinfrastructure nodes that communicate with a central controller. Thesensors operate at low power to conserve batteries, and increase thetime period in which batteries need to be replaced. This implies thatthe radio frequency (RF) signal generated by a sensor will haveextremely low signal strength. The infrastructure nodes are placedthroughout the network of sensors and they relay the data from thesensors to the central controller. The infrastructure nodes may be linepowered and they may communicate with each other and with the controllerat higher signal strength and also at a higher data rate. The RF linksbetween the leaf nodes and the infrastructure nodes as well as the RFlinks between the infrastructure nodes are highly susceptible tointerference and propagation effects, especially in indoor wirelessenvironments. These effects adversely affect the reliability of theentire wireless network.

Robust wireless communication, in the presence of electromagneticinterference (EMI), along with low power consumption by battery poweredsensor nodes are important considerations for designing wireless sensornetworks for industrial applications. For the proper functioning of theindustrial application, the data from the sensors has to be deliveredreliably and in a timely manner to the central controller.

SUMMARY OF THE INVENTION

Redundant, non-overlapping paths or routes for a wireless leaf nodesignal in a mesh network are selected, taking into account predeterminedmetrics of each route. In one embodiment, a wireless leaf node transmitsa signal that is received by two separate infrastructure nodes in themesh network. The signal is retransmitted by the two infrastructurenodes via the selected non-overlapping routes to a controller node.

Many signal routes to the controller may be discovered or identifiedwhen a leaf node is added to the network. Routes are identified for atleast two infrastructure nodes that receive signals from the added leafnode. Performance metrics are calculated for each route. The two routeswith the best performance metrics are selected in one embodiment.

In one embodiment the performance metrics include bandwidth utilizationpercentage of the infrastructure nodes on the path. Further metrics mayinclude number of hops in the path and cumulative RF link quality of theentire path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless mesh network according to anembodiment of the invention.

FIG. 2 is a block diagram of a typical leaf node according to an exampleembodiment.

FIG. 3 is a block diagram of a typical infrastructure node according toan example embodiment.

FIG. 4 is a block diagram representation of an information packet passedover a wireless mesh network according to an example embodiment.

FIG. 5 is a flowchart that illustrates route discovery, and generationof a routing table that includes non-overlapping route or path selectionaccording to an example embodiment.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, reference is made to the accompanyingdrawings that form a part hereof, and in which is shown by way ofillustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and thatstructural, logical and electrical changes may be made without departingfrom the scope of the present invention. The following description is,therefore, not to be taken in a limited sense, and the scope of thepresent invention is defined by the appended claims.

The functions or algorithms described herein are implemented in softwareor a combination of software and human implemented procedures in oneembodiment. The software comprises computer executable instructionsstored on computer readable media such as memory or other type ofstorage devices. The term “computer readable media” is also used torepresent carrier waves on which the software is transmitted. Further,such functions correspond to modules, which are software, hardware,firmware or any combination thereof. Multiple functions are performed inone or more modules as desired, and the embodiments described are merelyexamples. The software is executed on a digital signal processor, ASIC,microprocessor, or other type of processor operating on a computersystem, such as a personal computer, server or other computer system.Implementation of the functions may be distributed between differentcomponents in a network.

FIG. 1 shows a wireless network generally at 100. The wireless networkin one embodiment comprises a number of intermediate nodes 110, 112,114, 116, 118, 120, 122, 124, 126 and 128, also referred to asinfrastructure nodes. The infrastructure nodes are coupled to a centralcontrol 135 through gateways 175 and 180. Associated with theinfrastructure nodes are a plurality of wireless nodes 140, 142, 144,146, 148, 150, 152, and 154. The wireless nodes may be leaf nodes in oneembodiment that contain a sensor. The wireless nodes are referred to asa first tier network of nodes. The first tier of nodes communicates withthe infrastructure nodes. In one embodiment, they do not undertake anyrouting activities, i.e. any given tier 1 node does not store andforward messages from any other node in the network.

Infrastructure nodes may be coupled by a high power connection asindicated at 160. Any connection that provides suitable communicationscapabilities are within the meaning of connections 160. In oneembodiment, the high power connection 160 may be in the form of awireless connection, such as long range RF. The infrastructure nodes arealso coupled to the central control 135 via connections 160. Connections160 are shown in one particular arrangement, but are not intended to belimited to this type of arrangement. The infrastructure nodes arereferred to as a second tier network of nodes, including theircommunications with the central control 135. The central control 135 maybe connected to two or more infrastructure nodes, such as infrastructurenodes 112, 126 and 128. In one embodiment, the control center hasredundant gateways that receive signals from infrastructure nodes, suchthat even the control center itself has redundancy. These gateways maybe hardwire connections 175, 180, or transceivers, such as RFtransceivers represented by the same reference numbers.

Wireless nodes transmit signals as represented by lines 170 emanatingtoward selected infrastructure nodes. For instance, wireless node 140 isshown as transmitting a signal in multiple directions as represented bylines 170. Lines 170 shows two infrastructure nodes, 112 and 116 asreceiving a signal transmitted by wireless node 140. Otherinfrastructure nodes may be within range, but in one embodiment, theinfrastructure nodes closer to the central control 135 are selected toreceive and forward the signals. In another embodiment, theinfrastructure nodes with the better RF link qualities are selected toreceive and forward the signals. Each wireless node in FIG. 1 isrepresented as having its signals received by more than oneinfrastructure node. Some wireless node signals are only received by twoinfrastructure nodes, such as wireless node 152. Wireless node 152 hasits signals only being received by infrastructure nodes 122 and 124.Further wireless nodes may have signals received by more than twoinfrastructure nodes in further embodiments.

While a limited number of wireless nodes are shown in FIG. 1 forsimplicity, it should be understood that each infrastructure node mayreceive signals from many more wireless nodes than represented. Largernumbers of infrastructure nodes may also be used in network 100.

The wireless leaf node is shown in further detail in FIG. 2 at 210. Theleaf node 210, in one embodiment comprises a device 212, such as amotion detector, glass breakage, pressure, temperature, humidity andcarbon monoxide sensor, or controller or actuator for control of motorsand light among other functions. The device 212 is coupled to a logiccircuit 214 which is further coupled to a low power, short rangetransceiver 216, which is powered by a battery 218 such as a standard1.5 to 3 volt battery or other power source, such as solar power in oneembodiment. In further embodiments, some wireless leaf nodes may beline-powered.

Logic 214 provides an indication of an event or feedback from device212, or the status of the device to the transceiver 216, which thentransmits information regarding the event. Device 212 may comprise acomparator to compare a sensed parameter with programmed limits. Thelimits can be set by the central control, logic 214, or can be hardwiredat manufacture time. Jumper switches can also be used to set the limits.When a limit is reached or passed, an event is tripped, and a logic oneor zero is provided in standard logic levels, or special low voltagelogic such as CMOS TTL to logic 214. The device 212 can also be of thetype that provide analog output. In that case, logic 214 also providedsuitable analog to digital conversion functions. Where device 212comprises some sort of control, logic 214 provides signals from thecentral control to device 212 in the proper format for execution of anaction identified by the signals.

The wireless leaf node 210 transmits at a low power. Each wireless nodeis desirably associated with at least two infrastructure nodes. In otherwords, it is located close enough to the associated infrastructure nodessuch that it's signal transmitted at low power can be adequatelyreceived simultaneously by the infrastructure nodes. In one embodiment,the wireless nodes are leaf nodes, but may be at any location within thenetwork.

The signals transmitted by the sensors or wireless nodes are desirablyreceived by multiple independent infrastructure nodes. Theinfrastructure nodes are spaced apart from each other, and more than oneof them can receive the signals transmitted by sensors associated with adifferent independent infrastructure node. The combination ofinfrastructure nodes and associated wireless nodes provide the abilityto cover/span a desired area and monitor and or control a desiredenvironment, such as an industrial process.

A typical infrastructure node is shown generally at 310 in FIG. 3.Infrastructure node 310 comprises a dual transceiver 312, which receivesand transmits on the first tier network at the frequency of transceiver216 to provide communications to and from multiple wireless nodes. Inone embodiment, the first tier network uses a standard communicationsprotocol, such as a TDMA (time division/demand multiple access) or CSMA(carrier-sense multiple access), with the protocol being implemented ina known manner either in the transceiver logic 216 or logic 214 for thewireless nodes, and being implemented in either the transceiver 312 or aprocessing unit 314 in the infrastructure nodes. Processing unit 314 isan ASIC (application specific integrated circuit) in one embodiment, andprovides data I/O functions for a high function device 318 such as anaudio or video transducer, control, actuator or keypad/display device,and also provides routing functions for the information flowing throughthe infrastructure node.

Transceiver 312 also comprises a second tier transceiver, whichtransmits and receives information to and from further infrastructurenodes and the central control 135. In one embodiment, a power supply 316is coupled to an external power source such as standard 110/220 volt ACpower. The power supply 316 may also be completely batter powered, runoff DC current, run off various international power levels, solar, orother supply. The power supply 316 thus provides more power than thebattery 218 in device 210. Higher function device 318 is of the typethat either requires more power than can easily be provided by battery,or requires higher data throughput that can only be convenientlyprovided by an infrastructure node 310.

The infrastructure nodes communicate with each other using a highbandwidth, long range means of communication. In one embodiment, a TDMAor CSMA based protocol can be used. In one embodiment, all theinfrastructure nodes are aligned in time via pulses received over thepower lines in the structure in which the monitoring system isinstalled. In further embodiments, timing pulses may be provided by acentral infrastructure node or central control, or they are providedvery accurate clocks, or other types of high bandwidth protocols may beused which do not require timing pulses.

An example embodiment of a block diagram representation of aninformation packet 408 passed over the multi tier network is shown inFIG. 4. A tier 1 node, or leaf node device id is indicated at 410,followed by an infrastructure node, or tier 2 node ID at 411. Toincrease reliability, multiple transmissions for redundancy or errordetection/correction coding can be employed, altering the appearance ofthe data steam. Likewise, encryption can be employed to limit unintendeduse/reception of the system's information. These capabilities can alsoensure that multiple different systems installed in close proximity toeach other, such as in a condominium complex, do not incorrectly receivemessages from adjacent installed systems.

The ids 410 and 411 are used in conjunction with a routing table toproperly route bidirectional communications over the network. FurtherIds are used to indicate further hops in the path to and from thecontrol center 135. Data is indicated at 412. Leaf node statusinformation is provided at 412, and infrastructure node statusinformation is provided at 414. Finally, a priority indication may beprovided at 416. The priority indication is optionally used to ensurethat a particularly important communication is transmitted prior toother communications.

The information packet 408 may also be at least partially encoded toprevent others from defeating a security system implementation orotherwise interfere with communications, enables the central control 135to determine the source of information received, and ensures thatinformation received from two different infrastructure nodes is indeedthe same/is corroborated.

Infrastructure nodes may also be coupled to a hardwired connection, suchas a bus. Control center 135 may be a process control type of personalcomputer or other computing device capable of controlling a process.

The signals transmitted by the leaf nodes are communicated back tocontrol center 135. The signals may travel through multipleinfrastructure nodes to arrive at the control center 135. In oneembodiment, the signals are relayed through non-overlapping routes tothe control center 135. Signals to be transmitted are said to have asource node, and a destination node. The source node may be a leaf nodeor the control center, and the destination node is either the controlcenter or a leaf node in one embodiment. Other nodes may also beoriginating or destination nodes.

In FIG. 1, one route for signals from leaf node 154 might be relatedthrough multiple hops, involving infrastructure nodes 124, 116 and 128to the control center 135. A second, non-overlapping route would runthrough infrastructure node 126 to the control center 135. The firstroute may utilize a hard wired connection between infrastructure node128 and control center 135, the second route may utilize a hard wiredconnection between 126 and 135. In one embodiment, the control centerhas redundant gateways that receive signals from infrastructure nodes,such that even the control center itself has redundancy. These gatewaysmay be hardwire connections 175, 180, or transceivers, such as RFtransceivers represented by the same reference numbers.

In one embodiment, the RF communications between nodes utilize frequencyhopping-spread spectrum communication protocols.

The combination of infrastructure nodes and leaf nodes comprise asecurity, control or monitoring system which can be used in a structure,such as a home or business. It can also be applied to process control,where the leaf nodes comprise standard home, small business, commercialand industrial sensors, identification tags, and actuators such asmotion detectors, glass breakage, pressure, temperature, humidity andcarbon monoxide sensors, as well as motors and switches controllingautomated systems, each equipped with a transceiver. The devices areplaced throughout a structure or area to be monitored, protected orcontrolled. Combinations of security and control can be easilyconfigured for a home or business in one embodiment of the system.

The infrastructure nodes communicate with each other in one embodimentover a relatively high bandwidth, using unlicensed Industrial ScientificMedical (ISM) band spread spectrum signal processors or transceiverssuch as those which operate in the 900 MHz, 2.4 GHz and 5.8 GHz bands offrequencies. This “tier 2” level of infrastructure nodes provides a highbandwidth communication medium over which information may be transmittedover relatively long distances and are regulated by regulatory agencies,but not licensed.

The leaf nodes, or “tier 1” nodes, are provided with low power and lowbandwidth, relatively inexpensive, short range, such as on the order ofapproximately 3 to 6 meters, single chip transceivers operating atunlicensed frequencies such as approximately 300 or 433 MHz, which arealso not directly licensed. Other frequencies may be also be used ifdesired, such as those used by the infrastructure nodes. Since they arelow power, they do not normally transmit long distances. When used tosense conditions, or control actions of further devices such as a motoror light switch in a structure, these leaf nodes are placed wheredesired, but proximate a router/infrastructure node within thetransmission range of the leaf node. The central control 135 is alsoplaced conveniently for the user of the structure, but will likely notbe close enough to all of the leaf nodes to adequately receive theirtransmissions. Infrastructure nodes are placed strategically within thestructure to receive transmissions from the proximately located leafnodes. The infrastructure nodes then forward information throughpotentially other infrastructure nodes to the central control.Information and commands from the central control are likewise routedback through the infrastructure nodes to the leaf nodes. A routing tableis used by the infrastructure nodes to correctly route the informationin the form of messages as shown in FIG. 4, in both directions.

In a further embodiment, a routing table is not required. The packetitself might contain information about the whole route, i.e. it willhave information about all the intermediate hops.

FIG. 5 is an example embodiment of a flowchart that illustrates routediscovery, and generation of a routing table that includesnon-overlapping route or path selection. Note that in some embodiments,communications may occur in both directions between the central control135 and leaf nodes. Thus, the routes may be thought of being between theleaf nodes and central control 135, but is commonly referred to as beingfrom a leaf node to the central control 135. Different elements of theflowchart may be implemented at an infrastructure node or at the centralcontrol 135. On initialization of the network, or addition of a leafnode, each infrastructure node detects 510 leaf nodes that aretransmitting signals within range at 210. A local router table iscreated that identifies the infrastructure node, and the leaf nodes fromwhich signals are clearly received at 512. The table is then transferredthrough other infrastructure nodes to the central control 135.

In one embodiment, a primary infrastructure node for a leaf nodecommunicates with the other infrastructure nodes that received the leafnode transmission to determine the routes that are already known asavailable from them to the control center. In further embodiments, theleaf node signal is received by multiple infrastructure nodes thatretransmit the reception with an indication that they retransmitted it.This process continues with each infrastructure node transmitting towardthe central control. When the retransmissions arrive at the centralcontrol, the paths they took are included, allowing the central controlto identify all the routes.

The central control 135 receives all the router tables, and creates amaster router table or tables based on supporting any pre-definedquality of service (QoS) or signal priority. The route discovery processcalculates redundant non-overlapping routes 514 from the new leaf nodeto the control center. Routes are non-overlapping if they do not shareany infrastructure nodes. Many different route discovery mechanisms maybe utilized, such as those used in Destination-Sequenced DistanceVectoring (DSDV), Dynamic Source Routing (DSR) and Ad-Hoc On DemandDistance Vectoring (AODV).

The route discovery process may be performed by the primaryinfrastructure node, the central control, or other nodes, or anycombination thereof in a distributed manner. The routes are calculatedafter taking into account the bandwidth utilization of all theintermediate infrastructure nodes for a route. This ensures that thereis no transmit buffer overflow, and so no leaf node message data packetsare lost during traversal of the routes.

Performance metrics for each route are calculated at 516. Theperformance metrics correspond to the quality of each route. Theperformance metric consists of the number of hops in the route, acumulative RF link quality of the entire route, and a cumulativebandwidth utilization percentage. At 518, two routes that arenon-overlapping and which have the best performance metric are selectedas primary and secondary routes for the sensor. In one embodiment, thedifferent metrics may be given different weights and then added toobtain the overall performance metric of a given route. The two routeswith the top two overall performance metrics are selected. It ispossible that some of these multiple routes have intermediateinfrastructure nodes that are already busy most of the time transmittingdata. Such paths are avoided by including the bandwidth utilizationpercentage in the performance metric. This ensures that there will notbe major bottlenecks along the route for the sensor data to reach thecontrol center, and transmit buffer overflows will be avoided at theintermediate infrastructure node level.

In one embodiment, the routes are selected to minimize the latencybetween the same message arriving by the non-overlapping routes, whiletaking the route quality into account. This is done by making sure thatthe primary and the secondary routes not only have the first and thesecond best performance metrics, but their performance metrics are alsoas close as possible to each other. When failures occur in one route orroute pair, the system does not automatically re-route therebypotentially propagating the fault (in terms of additional latency).Non-affected routes continue to behave as normal. In one embodiment,human intervention is required to either repair the failures or re-routearound the failures. When new routes are discovered, the latency ofprior established routes is not increased beyond a preset threshold. Theprior established routes may share a node with a newly proposed route.

In one embodiment, if the leaf node's signal is received by only oneinfrastructure node, then non-overlapping routes are calculated fromthis infrastructure node to the central control. In another embodiment,an infrastructure node may generate a signal, such as a sensor signal,that may need to be routed to the central control and so non-overlappingroutes are calculated from this infrastructure node to the centralcontrol.

1. A method of communicating a signal between a source node and adestination node in a network of nodes, the method comprising:discovering more than one path between the source node and thedestination node wherein at least one of the paths contains at least oneintermediate node, the intermediate node being capable of receiving andre-transmitting messages from other nodes; and sending a message overmore than one of the paths between the source node and the destinationnode.
 2. The method of claim 1, wherein at least two of the pathsbetween the source node and the destination node are non-overlapping. 3.The method of claim 1 wherein the paths are selected from a group of allpossible paths based on measured qualification criteria.
 4. The methodof claim 3, wherein the same paths are used for one or more subsequentmessages between the source node and the destination node.
 5. The methodof claim 4, wherein the qualification criteria are comprised ofcombinations of measured latency, number of hops, link quality of one ormore hops, and resource utilization at one or more nodes along the path.6. The method of claim 5, wherein the selected paths have end to endlatency values within specified limits.
 7. The method of claim 6 andfurther comprising: detecting a failure in a path from the source nodeto the destination node; and continuing to use paths from the sourcenode to the destination node that are not affected by the failure. 8.The method of claim 7 and further comprising discovering a new path fromthe source node to the destination node that does not increase thelatency beyond the specified limits for the selected paths between allpairs of source and destination nodes in the network of nodes.
 9. Themethod of claim 6, wherein at least two of the selected paths arenon-overlapping.
 10. The method of claim 9 and further comprising:detecting a failure in a path from the source node to the destinationnode; and continuing to use paths from the source node to thedestination node that are not affected by the failure.
 11. The method ofclaim 10 and further comprising discovering a new path from the sourcenode to the destination node that does not increase the latency beyondthe specified limits for the selected paths between all pairs of sourceand destination nodes in the network of nodes.
 12. The method of claim11 wherein the discovered new path is non-overlapping with the priorselected paths from the source node to the destination node that are notaffected by the failure.
 13. The method of claim 5, whereinqualification criteria are measured recurrently for each of the selectedpaths.
 14. The method of claim 13, wherein if the measured qualificationcriteria fail for a given selected path, a new path is determined. 15.The method of claim 3, wherein the path selection is recurring.
 16. Themethod of claim 1, wherein a subset of the nodes use wirelesscommunications.
 17. The method of claim 1 wherein the method is repeatedupon incremental addition of a new source or destination node.
 18. Amethod of communicating a message from a source node to more than onedestination node, the method comprising: discovering a plurality ofpaths from the source node to each of the destination nodes wherein thepaths may or may not contain intermediate nodes, and wherein theintermediate node is capable of receiving and re-transmitting messagesfrom other nodes; and sending the message over one or more paths fromthe source node to each of the destination nodes.
 19. The method ofclaim 18, wherein for any given destination node, there is at least onepath from the source node to the given destination node that isnon-overlapping with at least one path from the source node to each ofthe other destination nodes.
 20. The method of claim 18, wherein thepaths to each destination node are selected from all possible pathsbased on measured qualification criteria.
 21. The method of claim 20,wherein the same paths are used for one or more subsequent messagesbetween the source node and each of the destination nodes.
 22. Themethod of claim 21, wherein the qualification criteria are comprised ofcombinations of measured latency, number of hops, link quality of one ormore hops, and resource utilization at one or more nodes along the path.23. The method of claim 22, wherein the selected paths have end to endlatency values within specified limits.
 24. The method of claim 23 andfurther comprising: detecting a failure in a path from the source nodeto one of the destination nodes; and continuing to use paths from thesource node to each of the destination nodes that are not affected bythe failure.
 25. The method of claim 24 and further comprisingdiscovering a new path, from the source node to the destination node towhich the path has failed, that does not increase the latency beyond thespecified limits for the selected paths between the source node and alldestination nodes.
 26. The method of claim 23, wherein: the message fromthe source node is sent to each destination node using one path; and thepaths from the source node to each of the destination nodes arenon-overlapping.
 27. The method of claim 26 and further comprising:detecting a failure in a path from the source node to one of thedestination nodes; and continuing to use paths from the source node toeach of the destination nodes that are not affected by the failure. 28.The method of claim 27 and further comprising discovering a new path,from the source node to the destination node to which the path hasfailed, that does not increase the latency beyond the specified limitsfor the selected paths between the source node and all destinationnodes.
 29. The method of claim 28 wherein the discovered new path isnon-overlapping with the prior selected paths from the source node toeach of the destination nodes that are not affected by the failure. 30.The method of claim 22, wherein qualification criteria are measuredrecurrently for each of the selected paths.
 31. The method of claim 30,wherein if the measured qualification criteria fail for a given selectedpath, a new path is determined.
 32. The method of claim 20, wherein thepath selection is recurring.
 33. The method of claim 18, wherein asubset of the nodes use wireless communications.
 34. The method of claim18 wherein the method is repeated upon incremental addition of a newsource or destination node.
 35. A method of communicating a signalbetween a central control and a node in a network of nodes, the methodcomprising: selecting non-overlapping first and second paths between thenode and the central control; sending the signal over the first path;sending the signal over the second path such that the signals from bothpaths arrive at the central control or the node within a maximum latencytime.
 36. The method of claim 35 wherein each path comprises multiplehops.
 37. The method of claim 36 wherein each path comprises multiplewireless infrastructure nodes.
 38. The method of claim 35 wherein thesignal is generated by a wireless leaf node in a wireless network.
 39. Asystem comprising: multiple wireless leaf nodes; multiple wirelessinfrastructure nodes, wherein each leaf node communicates signals withtwo infrastructure nodes; a central control that receives and sendscommunications from selected infrastructure nodes; wherein the leafnodes provide signals to the infrastructure nodes that are forwarded tothe central control via the infrastructure nodes over non-overlappingpaths; and wherein the control center provides signals to theinfrastructure nodes that are forwarded to the leaf nodes via theinfrastructure nodes over non-overlapping paths.
 40. The system of claim39 wherein the infrastructure nodes provide the signal to the centralcontrol over the paths within a desired time.
 41. The system of claim 39wherein the infrastructure nodes provide the signal to the leaf nodeover the paths within a desired time.
 42. The system of claim 39,wherein the central control is wired to the selected infrastructurenodes.
 43. The system of claim 39, wherein the one of the selectedinfrastructure nodes is the central control.
 44. The system of claim 39,wherein a given infrastructure node provides signals that are forwardedto the central control via other infrastructure nodes overnon-overlapping paths.
 45. A system for communicating a signal to acentral control, the system comprising: means for sending the signalover a first path to the central control; means for sending the signalover a second path that is non-overlapping with the first path; andmeans for selecting the each path such that the signal arrives at thecentral control within a specified time.
 46. The system of claim 45wherein each path comprise multiple hops.
 47. The method of claim 45wherein each path comprise multiple wireless infrastructure nodes. 48.The system of claim 45 wherein the signal is generated by a wirelessleaf node in a wireless network.
 49. A method of selecting communicationpaths in a wireless mesh network having leaf nodes, infrastructure nodesand a central control, the method comprising: adding a leaf node to thenetwork; discovering routes between the new leaf node throughinfrastructure nodes to the central control; calculating a performancemetric for multiple discovered routes; and selecting non-overlappingroutes based on the performance metrics.
 50. The method of claim 49wherein the performance metrics include number of hops in the routes, acumulative RF link quality of an entire path, and a cumulative bandwidthutilization percentage.
 51. A method of selecting routes in a multi-tierwireless network having wireless leaf nodes and multiple infrastructurenodes, the method comprising: detecting a signal transmitted from a leafnode at multiple infrastructure nodes; passing information related todetected signals to a central control; determining non-overlappingroutes from the leaf node to the central control; calculatingperformance metrics for the non-overlapping routes; and selecting twonon-overlapping routes as a function of the performance metrics.
 52. Acomputer readable medium having instructions stored thereon forexecution on a computer to perform a method comprising: receivingrouting information from infrastructure nodes related to signalsdetected from a leaf node; determining non-overlapping routes from theleaf node to the central control; calculating performance metrics forthe non-overlapping routes; and selecting two non-overlapping routes asa function of the performance metrics.
 53. A system comprising: multiplewireless leaf nodes; multiple wireless infrastructure nodes, whereineach leaf node communicates signals with one or more infrastructurenodes; a central control that receives and sends communications fromselected infrastructure nodes; wherein the leaf nodes provide signals tothe infrastructure nodes that are forwarded to the central control byone of the one or more infrastructure nodes via other infrastructurenodes over non-overlapping paths; and wherein the control centerprovides signals to the infrastructure nodes that are forwarded to theleaf nodes via the infrastructure nodes over non-overlapping paths. 54.The system of claim 53 wherein the infrastructure nodes provide thesignal to the central control over the paths within a desired time. 55.The system of claim 53 wherein the infrastructure nodes provide thesignal to the leaf node over the paths within a desired time.